1. Field of the Invention
The present invention relates to an acid resistant capsule shell composition, an acid resistant capsule shell, and a process for preparing the acid resistant capsule shell.
2. Description of the Prior Art(s)
Capsules containing drugs and shells enclosing the drugs are widely applied in oral medication field. The capsules shells prevent the drugs from direct contact with gustatory organ to cause nausea, from decomposition by saliva, and from deterioration by moisture, air, or light. The capsules shells also delay the release time of the drugs.
The main component of the commercial capsules shell is gelatin; the commercial capsules are dissolved in gastric acid and release drugs at stomach. However, release of drugs such as nonsteroidal anti-inflammatory drugs at stomach may cause serious gastric side effects such as damage of gastric mucosa, gastrorrhagia, or gastric perforation.
A conventional acid resistant capsule shell is developed to enclose the drugs, such that the drugs are released under intestinal condition instead of gastric condition to mitigate the gastric side effects of the drugs. To prepare the general acid resistant capsule, one of the conventional processes prepares a general capsule shell, loads drugs in the general capsule shell, and coats an enteric film at the outer surface of the general capsule shell. The solubility of the enteric film varies with pH value, i.e., the enteric film is soluble in alkaline condition but insoluble in acidic condition. Hence, the general acid resistant capsule can resist the gastric condition and release the drugs under intestinal condition. The component of enteric film is cellulose acetate phthalate (abbreviated as CAP), hydroxypropyl methylcellulose phthalate (abbreviated as HPMCP), hydroxypropyl methylcellulose acetate succinate (abbreviated as HPMP-AS), acrylic copolymers, or shellac. Since the components are required to be dissolved in organic solvents in the preparation, the general acid resistant capsule usually has undesired organic solvent residues, and is also complicated to be prepared.
Another conventional process for preparing a general acid resistant capsule is double dipping method, which is refined from the conventional dip molding process. A pin is dipped into a gelatin solution and an enteric coating solution subsequently, and then dried to form a general acid resistant capsule shell. Finally, drugs are loaded in the general acid resistant capsule shell to form the general acid resistant capsule. However, the component of the enteric coating solution is same with the component of the enteric film mentioned in the above paragraph; hence, the general acid resistant capsule prepared by the double dipping method also has organic solvent residues. Besides, the equipment of the double dipping method is more expensive than the equipment of the conventional dip molding process; therefore the cost of preparing the general acid resistant capsule may increase.
As stated above, there is still a need to overcome the problems such as complex process, expensive equipments, and undesired organic solvent residues.